SYNTHESIS AND PHOTOLUMINESCENCE OF WEBLIKE AGGLOMERATION OF SILICA NANOPARTICLES

Silica nanoparticles, produced by laser vaporization of polycrystallin e silicon in a He/O-2 or Ar/O-2 atmosphere in a diffusion cloud chambe r, aggregate into a novel weblike microstructure. These aggregates are very porous and have a very large surface area (460 m(2)/g). Bright b lue photoluminescence from the nanoparticle silica has been observed u pon irradiation with UV light. The photoluminescence is explained by t he presence of intrinsic defects of the type Si(II)(0) in the amorphou s silica. It is proposed that the laser ablation of Si in oxygen as de scribed here results in a silica nanostructure with a large concentrat ion, especially at its internal surfaces, of this Si(II)(0) defect whi ch in turn gives rise to the observed bright photoluminescence. This m aterial could have special applications in optical devices and catalys is and as a polymer reinforcing agent.